Additive manufacturing using plasma transferred arc

Abstract

Additive manufacturing is a process used to fabricate and repair parts that have a complex geometry or need to be functionally graded. The technique involves depositing multiple layers to produce the component. The success of the procedure depends on the deposition technique used, the parameters selected, and the alloy deposited. The deposition conditions, such as temperature and protective atmosphere, determine whether cracking and oxidation of the deposited layers occur. In the present study, the potential of plasma transferred arc to produce thin walls by additive manufacturing was evaluated. Two nickel-based alloys were used on an Ni-based substrate: a γ′ precipitation-hardened alloy and a solid-solution-hardened alloy. During the study, the processing parameters required to produce a thin wall with each alloy were determined and the use of preheating at 300 °C was analyzed. The results showed that the chemical composition of the alloy being processed and preheating influence the geometry of the wall. A fine dendritic solidification structure exhibiting epitaxial growth between layers was observed. The precipitation-hardened alloy showed banding of a γ′ precipitate-rich region that caused oscillations in the hardness. Dilution with the substrate was the main factor affecting the hardness profile of the wall processed with the Ni-based solid-solution alloy, which did not change following post-deposition heat treatment. This study has shown that sound thin walls can be successfully processed by additive manufacturing using plasma transferred arc.